configure retention
| RETENTION_TAG_MODE | No public |
| RETENTION_TARGET | congfigure retention target cpu and/or tag |
| RETENTION_CLK_SEL | No public |
| RETENTION_DONE_WAIT | wait retention done cycle |
| RETENTION_CLKOFF_WAIT | wait clk off cycle |
| RETENTION_EN | enable retention |
| RETENTION_WAIT | wait cycles for rention operation |